Most all metal implants are constructed of cobalt and chromium, although many have a titanium stem (another potential problem regarding mismatched metals). Patients with particular sensitivities to cobalt and chromium may experience significant adverse health effects at relatively low levels of metal exposure while others may have dangerously high levels of cobalt and chromium, yet remain asymptomatic. While cobalt and chromium toxicity have many of the same symptoms, there are important differences as well...

Nearly half a century after the first clumsy attempt at replacing a hip joint, an American surgeon at Johns Hopkins hospital and an American surgeon implanted a femoral replacement with a large, fixed head, made of Vitallium—a cobalt and chromium alloy.

Following the Stryker hip replacement recall in July, 2012, more questions have arisen regarding the formation of pseudotumors, metal poisoning and chromium and cobalt toxicity. Hip implant problems have rapidly become the rule rather than the exception, particularly among those with all-metal implants or implants such as the Rejuvenate and ABG II which have metal components. Research has indicated that pseudotumors are also much more likely among those with hip implants which contain chromium or cobalt. In one analysis, the only significant predictor for pseudotumors was serum cobalt levels above 5 µ/ml; patients with elevated cobalt levels were four times more likely to develop pseudotumors than those with lower levels after adjusting for age, gender, allergies and other factors.